1. Field of the Invention
The present invention relates to a method of and an apparatus for the inspection of vehicle wheel alignment and, more particularly, to methods and apparatus using cameras for the inspection of vehicle wheel alignment.
2. Description of the Related Art
In U.S. Pat. No. 5,535,522, issued Jul. 16, 1996 to Bernie F. Jackson, there is disclosed an apparatus for determining the alignment of a motor vehicle's wheels which comprises optical sensing means such as a pair of video cameras, an electronic processing means connected to the optical sensing mean, targets which either form parts of the wheels or are attached thereto and a display for indicating the detected alignment. In operation of this prior art system, the cameras are employed to provide images of the targets on the wheels, and the images are processed by the electronic processing means to provide an indication of the alignment or misalignment of the wheels.
Such inspection requires the targets to be kept within the fields of view of the cameras. However, during the correction of the alignment of the wheels of a vehicle, it is usually necessary to perform work underneath the vehicle and also at e.g. waist height. Consequently, it is necessary to raise and lower the vehicle. This has required corresponding raising and lowering of the cameras. For this purpose, the cameras were normally mounted on a boom provided with a hydraulic or other means for raising and lowering the boom and, therewith, the cameras.
This arrangement has a number of disadvantages. Firstly, the provision of the cameras with a camera boom and the means for raising and lowering the camera boom are relatively expensive, and considerable energy is utilized in raising and lowering the boom. Also, when the camera boom is in a lowered position, it becomes a hazard for people who risk walking into the boom and knocking their heads on the boom. Lowering of the camera boom produces the hazard that something or someone might be accidentally crashed below the boom. In addition, since it is necessary to leave an area free below the boom, that area is wasted.